DONT MERGE: CI: add testcase: separate etcd with calico

Calico use etcd directly by default, and we're not currently testing the
usecase where etcd|control-plane|node are separate with node access to
etcd.

Using opensuse because it's under represented in the CI.

----
Trying to match the reporter env

.gitlab-ci/packet.yml

@@ -125,6 +125,9 @@ packet_amazon-linux-2-all-in-one:
 packet_opensuse-docker-cilium:
   extends: .packet_pr
 
+packet_debian12-calico-sep:
+  extends: .packet_pr
+
 packet_ubuntu20-cilium-sep:
   extends: .packet_pr
 

tests/files/packet_debian12-calico-sep.yml

@@ -0,0 +1,8 @@
+---
+# Instance settings
+cloud_image: debian-12
+mode: separate
+
+kube_network_plugin: calico
+
+container_manager: containerd